Hi everyone,
Need some help with the following, please.

Background info.
shift pattern in (1) 07:00-14:00, (2) 14:00-22:00, (3) 22:00-7:00, (4) 14:00-07:00
now if you work a bank holiday you get one extra holiday as per the following
from above
(1) gains 1 extra day
(2) gains 1 extra day
(3) gains 1 extra day
(4) gains 2 extra days

that's easy to work out however i need the formula to also look at the day before. To cover the following
example
Date Start End
24/12 22:00 07:00 - that would be 07:00 on the 25th
25/12 14:00 07:00 - that would be 07:00 on the 26th
in the above example they would gain 3 extra days. 1 because they work up to 7:00 on the 25th plus 2 because they work from 14:00 on the 25th till 07:00 on the 26th.

how do i work this out?

I know how to work out when a bank holiday falls each year but what i can't solve the above, when looking at two different days.

Any help would be appreciated.